In general, power toothbrushes for cleaning teeth, including plaque removal, are well known. Typically, such power toothbrushes rely on a set of bristles attached to a bristle mounting plate which is moved by a driver to scrub the surfaces of the teeth. There are various known bristle configurations which are designed to effectively scrub exposed surfaces on the teeth, as well as to reach to some extent between the teeth or just under the gum line. Such brushing devices which rely on the scrubbing action of bristles for cleaning typically require significant pressure exerted by the user against the teeth to accommodate the differences in the shapes of the various teeth and to effectively clean the teeth. However, such pressure exerted against the teeth by the bristles typically results in a significant abrasion effect, including damage to both the soft and hard tissues in the mouth. This is of course undesirable, but often unavoidable to obtain the desired cleansing.
There are also limitations on the size (length and diameter) of the bristles insofar as while a small size may be desirable to reach between the teeth and under the gum line, the bristles still must be stiff enough to effectively scrub the teeth. Hence, with respect to a bristle-type toothbrush, effective cleaning is important but it is also desirable that as light a pressure as possible on the bristles be used, to reduce abrasion and tissue damage.
In addition, ultrasonic energy is used, either alone, or in addition to bristle action, to clean plaque from teeth. However, the level of ultrasonic energy used in the mouth is typically too low to be effective for plaque removal if reasonable safety is to be maintained.
Still other toothbrushes, particularly those using a resonant system, produce some degree of acoustic action by moving fluids in the mouth by the action of the moving bristles at the resonant frequency of the toothbrush. However, the resonant frequency of such a toothbrush is typically not the most effective frequency for all areas of the mouth. Further, the acoustic effect of such devices, produced by the bristle action, is typically not sufficient by itself to produce a clinically effective cleansing action. Such devices still rely to a significant extent on the scrubbing action of the bristles for cleaning.
The fact that the bristles themselves create the limited acoustic effect described above is significant relative to the effectiveness of the acoustic action. Increasing the amount of acoustic energy generated, in order to make that portion of the cleansing action more effective, will result in increased bristle motion and tissue abrasion. Further, providing additional power to increase the acoustic effect will result in additional bulk and cost to the device.
Hence, it is desirable to have a toothbrush which effectively cleans teeth, including the hard to reach areas, such as between the teeth and under the gum line, which relies primarily on acoustic action not produced by bristle movement.